1. Field of the Invention
The present invention relates to a substance shutoff device for shutting down the communication of an inflammable substance or oxidizer, and to a fuel cell provided with means for shutting down the communication of a fuel or oxidizer.
2. Related Background Art
A conventional leak detection/shutoff device for an inflammable gas is constructed with a detection mechanism for detecting a gas leak; a control mechanism for giving an order to shut down the gas based on detection signals; and shutoff means for shutting down the gas. The mechanisms and the means are each driven by receiving energy, such as electricity, supplied from outside of the device.
Meanwhile, an example of an inflammable gas detection mechanism is a device employing a semiconductor device. Another example thereof is a device disclosed in Japanese Patent Application Laid-Open No. 2004-028749, in which heat generated by combustion of an inflammable gas in a catalyst portion is converted into a voltage signal through a thermoelectric conversion effect, which is used as a detection signal. Further, as a gas shutoff means, there is often employed a valve, which opens/closes by using electricity, such as an electromagnetic valve. A method is also employed in which the gas shutoff operates by heat. Examples of the heat operated gas shutoff means include a fuse mechanism disclosed in Japanese Patent Application Laid-Open No. 2000-002354, in which a bearing member loses a bearing power by heat so that a valve member seats on a valve seat, and a device disclosed in Japanese Patent Application Laid-Open No. H07-071634, in which a substance, which has softened to deform or has become a viscous fluid by heat, fills in pores of a heat resistant porous material to close a gas flow path. Japanese Patent Application Laid-Open No. 2000-046219 discloses a pressure regulator provided with a thermal fuse. Further, an example of a device, which uses heat of catalytic combustion to operate shutoff means for a gas flow path, is a catalytic combustion hot air device disclosed in Japanese Patent Application Laid-Open No. H06-154022.
Meanwhile, as disclosed in Japanese Patent Application Laid-Open No. H08-315847, a fuel cell is provided with a fuel detection sensor as a safety measure against a fuel leak. The fuel cell is provided with a shutoff means for shutting down the supply of a fuel to a fuel cell body when the fuel leaks, or a discharge means for discharging the fuel out of a case. Further, examples of fuel detection for a fuel cell that have been attempted include a method involving fuel detection by deterioration in power generation characteristics of a fuel cell, and a method involving mixing of an odorant substance or a detecting substance, such as helium, in a gaseous fuel. In addition, an electromagnetic valve or the like is used for fuel shutoff means.
However, the conventional detection means for an inflammable substance involves conversion of a detection signal into an electrical signal for processing, and thus requires a processing circuit and a power source for driving the processing circuit. Further, the shutoff means employing an electromagnetic valve or the like requires a power source for driving the valve. Further, the shutoff means that operates by heat is mostly used for preventing the heating of a system, and no shutoff means is directly connected to a detection mechanism for a leaking substance. Moreover, those systems each have problems in that have a complicated structure and a large size.
Until now, no fuel cell has utilized heat generation associated with catalytic combustion for the detection of a fuel leak. Further, no fuel cell has utilized heat generation associated with catalytic combustion in a power generation cell of a fuel cell for the detection of a fuel leak. Moreover, no fuel cell has utilized a shutoff means driven by heat for shutting down a leaking substance.